diff --git a/apps/dashboard/src/components/create-run-form.tsx b/apps/dashboard/src/components/create-run-form.tsx
index b9417964..ee029174 100644
--- a/apps/dashboard/src/components/create-run-form.tsx
+++ b/apps/dashboard/src/components/create-run-form.tsx
@@ -45,6 +45,7 @@ export function CreateRunForm({ onCancel, onSuccess }: CreateRunFormProps) {
   const [workflowName, setWorkflowName] = useState("");
   const [version, setVersion] = useState("");
   const [input, setInput] = useState("");
+  const [idempotencyKey, setIdempotencyKey] = useState("");
   const [availableAt, setAvailableAt] = useState("");
   const [deadlineAt, setDeadlineAt] = useState("");
   const [inputError, setInputError] = useState<string | null>(null);
@@ -94,6 +95,7 @@ export function CreateRunForm({ onCancel, onSuccess }: CreateRunFormProps) {
           workflowName: workflowName.trim(),
           version: normalizeOptionalField(version),
           input: normalizedInput,
+          idempotencyKey: idempotencyKey || null,
           availableAt: availableAtIso,
           deadlineAt: deadlineAtIso,
         },
@@ -165,6 +167,29 @@ export function CreateRunForm({ onCancel, onSuccess }: CreateRunFormProps) {
             <FieldError>{inputError}</FieldError>
           </Field>
 
+          <Field>
+            <FieldLabel htmlFor="create-run-idempotency-key">
+              Idempotency Key
+            </FieldLabel>
+            <Input
+              id="create-run-idempotency-key"
+              name="idempotencyKey"
+              value={idempotencyKey}
+              onChange={(event) => {
+                setIdempotencyKey(event.currentTarget.value);
+              }}
+              placeholder="e.g. welcome-email:user_123"
+              aria-describedby="create-run-idempotency-key-description"
+              autoComplete="off"
+              disabled={isSubmitting}
+            />
+            <FieldDescription id="create-run-idempotency-key-description">
+              Reusing a key for the same workflow name in this namespace opens
+              the existing run for 24 hours after creation, even with different
+              input or version. Leave empty to create a new run.
+            </FieldDescription>
+          </Field>
+
           <div className="grid gap-5 sm:grid-cols-2">
             <Field>
               <FieldLabel htmlFor="create-run-available-at">
diff --git a/apps/dashboard/src/lib/api.ts b/apps/dashboard/src/lib/api.ts
index 6ad1832f..a3e36aec 100644
--- a/apps/dashboard/src/lib/api.ts
+++ b/apps/dashboard/src/lib/api.ts
@@ -149,6 +149,7 @@ export const createWorkflowRunServerFn = createServerFn({ method: "POST" })
       workflowName: z.string().trim().min(1),
       version: z.string().nullable().optional(),
       input: z.string().nullable().optional(),
+      idempotencyKey: z.string().nullable().optional(),
       availableAt: z.string().nullable().optional(),
       deadlineAt: z.string().nullable().optional(),
     }),
@@ -166,7 +167,8 @@ export const createWorkflowRunServerFn = createServerFn({ method: "POST" })
     return backend.createWorkflowRun({
       workflowName: data.workflowName,
       version,
-      idempotencyKey: null,
+      idempotencyKey:
+        data.idempotencyKey === "" ? null : (data.idempotencyKey ?? null),
       config: {},
       context: null,
       input: parseWorkflowInput(data.input),
diff --git a/apps/dashboard/src/routes/runs/$runId.tsx b/apps/dashboard/src/routes/runs/$runId.tsx
index da70d64e..25124284 100644
--- a/apps/dashboard/src/routes/runs/$runId.tsx
+++ b/apps/dashboard/src/routes/runs/$runId.tsx
@@ -535,6 +535,17 @@ function RunOverviewPanel({
           <span className="text-muted-foreground shrink-0 text-xs">Run ID</span>
           <IdentifierValue value={run.id} />
         </div>
+        {run.idempotencyKey !== null && (
+          <div className="flex min-w-0 flex-wrap items-center gap-2">
+            <span className="text-muted-foreground shrink-0 text-xs">
+              Idempotency Key
+            </span>
+            <IdentifierValue
+              value={run.idempotencyKey}
+              className="whitespace-pre-wrap"
+            />
+          </div>
+        )}
         <div className="flex min-w-0 flex-wrap items-center gap-2">
           <span className="text-muted-foreground shrink-0 text-xs">Status</span>
           <Tooltip>